Chiral H-aggregation-induced large stokes shift with CPL generation assisted by α-helical poly(L-lysine) substructure

Fluorescent materials with large Stokes shifts have significant potential for use in optical applications. Typically, a synthetic design strategy is utilized for this purpose. In this study, we demonstrated a novel method by binding a chiral template to a nonchiral fluorescent agent without chemical modification. Specifically, α-helical poly(L-lysine) was employed as the chiral template, which interacted with a disulfonic fluorescent dye, such as NK2751. The dye caused excimer luminescence by inducing the formation of a chirally H-aggregated dimer only when poly(L-lysine) was in an α-helical shape. The result was a Stokes shift of 230 nm. Similar effects were not observed when the chiral template was in a random coil condition and the Stokes shift was less than 40 nm. These findings imply that H-aggregated dimerization, which often results in quenching, permits the electronic transitions necessary for fluorescence events by the formation of the chirally twisted state. In addition, we introduce for the first time the generation of circularly polarized luminescence using the chirality induction phenomena in a dye supported by poly(L-lysine).

Construction of Artificial Light-Harvesting Systems Based on Aggregation-Induced Emission Type Supramolecular Self-Assembly Metallogels

A method for preparing new artificial light-harvesting systems (ALHSs) based on supramolecular metallogels was proposed. Various metal ions were introduced into a solution of a bi-benzimidazole compound (P) in ethylene glycol, and P exhibited high selectivity toward Al3+, as indicated by the noticeable red shift (49 nm) observed in the fluorescence spectra of P after the addition of Al3+. Interestingly, the gelator, P, could self-assemble into a stable supramolecular gel (P-gel) that exhibits strong aggregation-induced emission in ethylene glycol. Thus, two ALHSs were successfully prepared in a gel environment. The P-Al3+ assembly acts as the donor in the ALHSs, while BODIPY 505/515 (BDP) and rhodamine 6G (Rh6G), which are loaded onto the P-Al3+ assembly, act as acceptors. In these two diverse systems, the occurrence of an energy transfer process is confirmed from the P-Al3+ assembly to BDP and Rh6G. The findings of this study will enable the design and fabrication of ALHSs.

Inversion of Supramolecular Chirality by In Situ Hydrolyzation of Achiral Diethylene Glycol Motifs

Chiral inversion of supramolecular assemblies is of great research interest due to its broad practical applications. However, chiral structure transition induced by in situ regulation of building molecules has remained a challenge. Herein, left-handed fibrous assemblies were constructed by C₂-symmetic l-phenylalanine coupled with diethylene glycol (LPFEG) molecules. In situ hydrolyzing terminal diethylene glycol motifs in LPFEG successfully inverted the chirality of the nanofibers from left- to right-handedness. The transition of right-handed fibers into left-handed fibers could also be achieved via hydrolyzing DPFEG molecules. Circular dichroism (CD) spectroscopy, 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy revealed that the back-folded achiral diethylene glycol played a vital role in L/DPFEG molecular arrangements and removing terminal diethylene glycol could induce the opposite rotation of molecular assemblies. Thanks to this merit, the enantioselective separation of racemic phenylalanine was obtained and the enantiomeric excess (ee) values could achieve around ±20% after separation. This study not only provides a new strategy to regulate the chiral structure via dynamic modulation of terminal substituents but also presents a promising application in the field of enantioselective separation.

Molecular Encapsulation of Naphthalene Diimide (NDI) Based π-Conjugated Polymers: A Tool for Understanding Photoluminescence

Conjugated polymers are an important class of chromophores for optoelectronic devices. Understanding and controlling their excited state properties, in particular, radiative and non-radiative recombination processes are among the greatest challenges that must be overcome. We report the synthesis and characterization of a molecularly encapsulated naphthalene diimide-based polymer, one of the most successfully used motifs, and explore its structural and optical properties. The molecular encapsulation enables a detailed understanding of the effect of interpolymer interactions. We reveal that the non-encapsulated analogue P(NDI-2OD-T) undergoes aggregation enhanced emission; an effect that is suppressed upon encapsulation due to an increasing π-interchain stacking distance. This suggests that decreasing π-stacking distances may be an attractive method to enhance the radiative properties of conjugated polymers in contrast to the current paradigm where it is viewed as a source of optical quenching.

Semiconductive coordination polymers with continuous π-π interactions and defined crystal structures

Two semiconductive coordination polymers based on a chelating redox-active ligand were synthesized and structurally characterized. Strong and continuous intermolecular π-π interactions are likely the reason for moderate electrical conductivity of about 10^-5 S m^-1 in these materials. The results of DFT calculations indicate that the continuous π-π stacking structure contributes to the orbital overlap and thus improves charge transport performance.

Tuning of the optoelectronic properties of peptide-appended core-substituted naphthalenediimides: the role of self-assembly of two positional isomers

This study demonstrates how the self-assembly pattern of two different and isomeric peptide-appended core-substituted naphthalenediimides (NDIs) affects the modulation of their optoelectronic properties. Two isomeric peptide-attached NDIs were synthesized, purified and characterized. Interchanging the position of attachment of the peptide units and the alkyl chains in the NDI has altered the respective self-assembling patterns of these isomeric molecules in the aggregated states. The isomer having a peptide moiety in the core position and the alkyl chain in the imide position (compound N1) forms face to face stacking or 'H' aggregates in aliphatic solvents including n-hexane, and n-decane, whereas compound N2, in which the peptide moiety is at the imide position and the alkyl chain is attached at the core position of NDI exhibits edge to edge stacking or J aggregates under the same conditions as it is evident from their UV-vis studies. The H aggregated species (obtained from N1) show inter-connected nanofibers, whereas the J aggregated species (obtained from N2) exhibit the morphology of helical nanoribbons. FT-IR and X-ray diffraction studies are in favor of the same aggregation behavior. The individual packing patterns of these two peptide-based isomers have a direct impact on their respective electrical conductivity. Interestingly, the H aggregated species shows 100 times greater current conductivity than that of the J aggregate. Moreover, it is only the H aggregated species that exhibits a photocurrent, and no such photocurrent response is observed with the J aggregates. Computational studies also support that different types of aggregation patterns are formed by these two isomeric molecules in the same solvent system. This unique example of tuning of optoelectronic behavior holds future promise for the development of new peptide-conjugated π-functional materials.

The aging effect on the enhancement of thermal stability, mechanical stiffness and fluorescence properties of histidine-appended naphthalenediimide based two-component hydrogels

A histidine attached naphthalenediimide (NDI)-containing amphiphilic molecule (NDIP) self-assembles into nanotubes in aqueous solution at pH 6.6 as revealed by high-resolution transmission electron microscopy studies. This histidine-appended NDI forms a two-component hydrogel in the presence of tartaric acid at a molar ratio of 1 : 2. A morphological transformation was observed from a nanotube structure in the non-gel aggregated state of histidine appended NDI to interconnected cross-linked nanofibers of the two-component hydrogel in the presence of tartaric acid. Interestingly, the gel exhibits an unusual behavior upon aging compared to the fresh gel. It is found that the thermal stability and gel stiffness increase very significantly upon aging. Another important feature noted is that the very weak fluorescence of the fresh gel is transformed into bright greenish fluorescence upon aging. These results suggest that intermolecular interactions among the gelator molecules and tartaric acid in the gel phase slowly increase with time to form a mechanically very stiff and thermally robust gel.

Electronically Coupled Gold Nanoclusters Render Deep-Red Emission with High Quantum Yields

Electronic coupling can be used to tailor electronic states and optical properties of the luminophores. Therefore, electronically coupled systems would provide unique properties, which cannot be achieved by individual constituents. Here, electronically coupled gold nanoclusters (AuNCs) were prepared on the basis of organosilane grafting and a sol-gel-derived porous silica template. After prolonged drying, the formed AuNCs@silica composites exhibited red-shifted, line-width-narrowed, deep-red emission with high quantum yields (QYs) of ∼66% due to electronic-coupling-enhanced radiative rates and covalent-bonding-suppressed nonradiative relaxation. Meanwhile, the absorption maximum was slightly blue-shifted, leading to a large Stokes shift. All experimental findings revealed the formation of electronically coupled AuNC aggregates confined inside the nanopores and bonded to silica matrix. The mechanism is distinctly different from conventional aggregation-enhanced emission. Our work would provide great potential to engineer photophysical properties by controlling the packing modes.

A Self-Assembled Peptide-Appended Naphthalene Diimide: A Fluorescent Switch for Sensing Acid and Base Vapors

A histidine-containing bola-amphiphilic molecule (NDIP) containing a peptide-appended naphthalenediimide (NDI) forms fluorescent hydrogels in phosphate buffer and organogels with benzenoid solvents. These gels were characterized by several spectroscopic and microscopic techniques including FT-IR, HR-TEM, powder X-ray diffraction and small-angle X-ray scattering, UV-Vis and fluorescence studies. The gelator molecule exhibits no significant fluorescence in the xerogel state, while it shows a significant fluorescence (bright cyan) in the presence of volatile organic/inorganic acid vapors; this cyan color vanishes in presence of base (ammonia vapors). A reusable paper-strip-based method based on this self-assembled fluorescent material can be used to easily detect hazardous volatile acid and base vapors with the naked eye.

Molecular Phosphorescence in Polymer Matrix with Reversible Sensitivity

Ultralong organic phosphorescence strongly depends on the formation of aggregation, while it is difficult to obtain in dilute environments on account of excessive internal and external molecular motions. Herein, ultralong single-molecule phosphorescence (USMP) at room temperature was achieved in the monomer state by coassembling biphenyl and naphthalene derivatives at low density with poly(vinyl alcohol) (PVA), where PVA provides a confined environment to stabilize the triplet state. Various factors that affect the USMP were studied, including aggregation, conformation, temperature, and moisture. In these systems, the formation of aggregates through intermolecular stacking and hydrogen bonding interactions in the film or crystal phases completely suppresses the USMP. However, the fluorescence is enhanced when coassembling these compounds at high concentration with PVA and becomes stronger in their powder state, indicating that the intersystem crossing process is blocked by the aggregation. Theoretical calculations suggest that the aggregation depresses spin-orbit coupling between the excited singlet and triplet states and enhances the nonradiative quenching process. Moreover, a relatively twisted conformation is more conducive to the occurrence of intersystem crossing than planar conformation. The USMP shows delicate and reversible sensitivity to the changes of temperature and moisture, rendering them with the applicability as smart organic optoelectronic materials.

Effect of Chirality on Cell Spreading and Differentiation: From Chiral Molecules to Chiral Self-Assembly

The influence of chirality on cell behavior is closely related with relevant biological events; however, many recent studies only focus on the apparent chiral influence of supramolecular nanofibers and ignore the respective effects of molecular chirality and supramolecular chirality in biological processes. Herein, the inherent molecular and supramolecular chiral effects on cell spreading and differentiation are studied. Left-handed nanofibers (referring to supramolecular chirality) assembled from l-amino acid derivatives can enhance cell spreading and proliferation compared to flat l-surfaces (referring to molecular chirality). However, compared to the d-surfaces (referring to molecular chirality), right-handed nanofibers (referring to supramolecular chirality) derived from d-amino acid suppress cell spreading and proliferation, overturning the conventional view that a fibrous morphology generally enhances cell adhesion. The results directly suggest that the amplification of chirality from chiral molecules to chiral assemblies significantly enhances the effect on regulated cell behavior by supramolecular helical handedness. Moreover, cell differentiation is found to be chirality dependent. It suggests that both the l-amino acid derivatives and the left-handed fibers facilitate osteogenic differentiation. This study provides useful insight into understanding the origin of chiral expression from the molecular to the macroscopic level in nature.

Carboxylate-functionalized organic nanocrystals for high-capacity uranium sorbents

Carboxylate-functionalized organic nanocrystals (ONCs) derived from perylene diimide or naphthalene diimide were synthesized and carefully characterized as novel high-capacity uranium (U(VI)) sorbents. Adsorption studies using uranyl ions demonstrated that the carboxyl and hydroxyl groups on the surface of the ONCs play pivotal roles in U(VI) adsorption. ONCs formed from the condensation of perylene dianhydride and aminoisophthalic acid exhibit very high U(VI) adsorption capacities of 1393 mg g^-1 comparable to the highest capacity ever reported. The adsorption kinetics of the ONCs were found to obey the second-order model, indicating that chemisorption is the rate-determining step for U(VI) adsorption by these materials. Furthermore, the perylene-based ONC containing imidazole exhibited no pH dependency upon the U(VI) adsorption and the naphthalene-based ONC was able to remove up to 97.5% U(VI) from simulated nuclear industrial effluent containing many competing elements. These findings will facilitate the development of high-performance organic U(VI) sorbents with high densities of adsorption sites.

Assembly of amino acid containing naphthalene diimide-based molecules: the role of intervening amide groups in self-assembly, gelation, optical and semiconducting properties

Two naphthalene diimide containing molecules, one with a covalently linked peptide (P1) and the other with a covalently attached amino acid residue and a diamine moiety (P2), have been chosen in such a way that the number of intervening amide groups and the centrally located imide moieties are the same, and their molecular formulae are also identical. However, the positions of the amide groups are different in these two molecules and this can dictate a different behaviour in molecular assembly and gelation processes for each of the individual NDI-appended peptide (P1) and pseudo-peptide (P2). The molecule P1 with an attached peptide moiety and the intervening -CO-NH groups forms an organogel in a mixture of chloroform-methylcyclohexane at a very rapid rate and the mechanical strength of the gel is quite high, whereas the molecule P2, containing the amino acid and diamide moieties, and with the intervening -NH-CO groups forms an organogel in a relatively much slower rate in chloroform-methylcyclohexane mixture. The mechanical strength of the P2 gel is significantly lower compared to that of the P1 gel at the same concentration and solvent system. The minimum gelation concentration of P1 is much smaller than that of P2 in the same solvent system. The thermal stability of the P1 gel is higher than that of the P2 gel at the same concentration and solvent system. However, both of these gels form J-type aggregates in a mixture of chloroform-methylcyclohexane with a red shift in the UV-vis spectrum. The gelator P1 exhibits enhanced fluorescence compared to that of P2 at a fixed concentration and in the same solvent system (mixture of chloroform-methylcyclohexane, 5 : 95 (v/v)). The lifetime and quantum yield of the P1 gel are also significantly higher than those of the P2 gel under similar gelation conditions. Moreover, both P1 and P2 are found to exhibit significant semiconducting behaviours in their dried/xerogel states. It is important to note that the stronger gel P1 exhibits relatively better semiconducting behaviour than the weak gel P2. Interestingly, the self-assembly, gelation, photoluminescence and electrical conductivity are different for the gels obtained from these two molecules. This indicates the role of the amide bond and its linkage (whether -CONH/-NHCO) in the self-assembly, gelation and optoelectronic behaviour of these molecules in their assembled states.

Emissive intelligent supramolecular gel for highly selective sensing of Al3+ and writable soft material

A fluorine-containing acylhydrazone was newly designed and found to form gels in a mixed solvent of DMSO-ethylene glycol. The gelator could show brilliant blue light upon mixing with Al3+, which could be erased by F- ions and thus forming an erasable gel.

Injectable Hydrogel of Vitamin B9 for the Controlled Release of Both Hydrophilic and Hydrophobic Anticancer Drugs

Folic acid (FA), vitamin B₉ , is a good receptor of drugs triggering cellular uptake via endocytosis. FA is sparingly soluble in water. Herein, a new approach for the formation of FA hydrogel by the hydrolysis of glucono-δ-lactone in PBS buffer under physiological conditions has been reported. The gel has a fibrillar network morphology attributable to intermolecular H-bonding and π-stacking interactions. The thixotropic property of the gel is used for the encapsulation of both hydrophilic [doxorubicin (DOX)] and hydrophobic [camptothecin (CPT)] drugs. The loading of DOX and CPT into the gel is attributed to the H-bonding interaction between FA and drugs. The release of DOX is sustainable at pH 4 and 7, and the Peppas model indicates that at pH 7 the diffusion of the drug is Fickian but it is non-Fickian at pH 4. The release of CPT is monitored by fluorescence spectroscopy, which also corroborates the combined release of both drugs. The metylthiazolyldiphenyltetrazolium bromide assay of FA hydrogel demonstrates nontoxic behavior and that the cytotoxicity of the DOX-loaded FA hydrogel is higher than that of pure DOX, with a minimal effect on normal cells.

H- and J-aggregates formed from a nontraditional π-gelator depending on the solvent polarity for the detection of amine vapors

A tert-butyl carbazole-modified difluoroboron β-diketonate complex (TCbzB) has been synthesized. Although no traditional gelation group was involved in TCbzB, it could form organogels in the mixed solvents of o-dichlorobenzene/cyclohexane (v/v = 1/5 or 1/2), toluene/cyclohexane (v/v = 1/2) and chlorobenzene/cyclohexane (v/v = 1/2). Interestingly, an orange organogel was obtained in o-dichlorobenzene/cyclohexane (v/v = 1/2) with relatively high polarity and red organogels were gained in the other three mixed solvents with relatively low polarity. TCbzB self-assembled into H-aggregates and J-aggregates in orange and red organogels, respectively, and the corresponding xerogels emitted yellow and red light, respectively, under UV illumination. The red emission of the xerogel-based film could be quenched significantly by gaseous n-propylamine and aniline because of the decomplexation of the difluoroboron β-diketonate complex by n-propylamine and the weak interactions between aniline and boron difluoride units.

Solvent Control over Supramolecular Gel Formation and Fluorescence for a Highly Crystalline π-Conjugated Polymer

In π-conjugated polymers (πCPs), crystallinity and fluorescence typically exhibit a trade-off relationship. Here, we have synthesized a highly crystalline and fluorescent π-conjugated polymer with a simple alternating structure of 1,2,4,5-tetrafluorophenylene and 3,3'-dihexyl-2,2'-bithiophene units. In film, the polymer exhibited efficient red-colored fluorescence, an improved quantum yield (Φsol =13 %→Φfilm =23 %) and a crystalline structure. Interestingly, supramolecular gel formation occurred in appropriate solvents, and the macrostructure and fluorescence properties of the gel could be directly controlled by the choice of the solvent. The polymer self-assembled into a spherical form that exhibited red fluorescence in non-aromatic solvent (1,2-dichloroethane) and into a fibrous form that exhibited yellow fluorescence in aromatic solvent (mesitylene).

A room-temperature phosphorescent polymer film containing a molecular web based on one-dimensional chiral stacking of a simple luminophore

We propose a new approach for a totally organic, room-temperature phosphorescent system with a lifetime on the order of milliseconds, which is achieved by promotion of the one-dimensional chiral stacking of a simple, small fluorophore in a solution state. The versatility of this system is highlighted by its good applicability to the fabrication of a phosphorescent polymer film. This paper demonstrates the first example of a room-temperature phosphorescent polymer film prepared with our methodology.

Luminescent Naphthalene Diimide-Based Peptide in Aqueous Medium and in Solid State: Rewritable Fluorescent Color Code

This study convincingly demonstrates a unique example of the self-assembly of a naphthalene diimide (NDI)-appended peptide into a fluorescent J-aggregate in aqueous media. Moreover, this aggregated species shows a remarkable yellow fluorescence in solid state, an unusual phenomenon for NDI-based compounds. The aggregated species has been characterized using transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, X-ray diffraction, time-correlated single proton counting (TCSPC), UV-vis, and photoluminescence studies. TEM images reveal cross-linked nanofibrillar morphology of this aggregated species in water (pH 7.4). TCSPC study clearly indicates that the aggregated species in water has a higher average lifetime compared to that of the non-aggregated species. Interestingly, this NDI-based peptide shows H+ ion concentration-dependent change in the emission property in water. The fluorescence output is erased completely in the presence of an alkali, and it reappears in the presence of an acid, indicating its erasing and rewritable property. This indicates its probable use in authentication tools for security purposes as a rewritable fluorescence color code. This NDI-appended peptide-based molecule can be used for encryption of information due to erasing and rewritable property of the molecule in the aggregated state in aqueous medium.

Fluorescent nanofiber film based on a simple organogelator for highly efficient detection of TFA vapour

SYW showed a gelation-induced emission of light, and its gel showed a reversible response of its emission to trifluoroacetic acid vapour, with a detection limit of 3.2 ppb.

A novel thermo-responsive supramolecular organogel based on dual acylhydrazone: fluorescent detection for Al3+ ions

A new dual acylhydrazone-functionalized gelator (L) has been synthesized, which behaves as a thermal-responsive supramolecular organogel (L-gel) in DMSO. This L-gel exhibits very weak fluorescence based on the photoinduced electron transfer (PET) mechanism. The L-gel can recognize Al³⁺ and assemble into an enhanced blue-light-emitting supramolecular metallogel (Al@gel).

The anion impact on the self-assembly of naphthalene diimide diimidazolium salts

Self-assembly behavior of naphthalene diimide diimidazolium salts was analyzed as a function of their anions. Changes in the anion nature significantly impact the properties of aggregates.

Emission enhancement of GFP chromophore in aggregated state via combination of self-restricted effect and supramolecular host–guest complexation

The emission response of GFP chromophore in aggregated state is greatly enhanced more than 100-fold due to the inhibition of conformational motion and the reduction of strong π–π interaction.

Two-Component Fluorescent-Semiconducting Hydrogel from Naphthalene Diimide-Appended Peptide with Long-Chain Amines: Variation in Thermal and Mechanical Strengths of Gels

Two-component fluorescent hydrogels have been discovered, containing the mixtures of naphthalene diimide (NDI)-conjugated peptide-functionalized bola-amphiphile and primary amines with long alkyl chains at physiological pH 7.46. The aggregation-induced enhanced emission associated with an NDI-appended peptide in aqueous medium is rare, as water is known to be a good quencher of fluorescence. In this study, an NDI-containing gelator peptide forms a highly fluorescent aggregate in aqueous medium. Absorption and emission spectroscopic techniques reveal the formation of J-aggregates among the chromophoric moieties in their aggregated state in aqueous medium. However, this NDI-containing peptide does not form any gel in aqueous medium. In the presence of the primary amines with long alkyl chains in the buffer solution, it forms two-component fluorescent hydrogels exhibiting bright yellow fluorescence under a UV lamp (365 nm). Probably, the acid-amine interaction between the amines and the bola-amphiphile triggers the gel formation, as evident from Fourier transform infrared data, indicating the presence of a carboxylate group (-COO^-) and an ammonium species (NH₃⁺) in the coassembled two-component gel system. Low- and wide-angle powder X-ray diffraction and small-angle X-ray scattering further support the fact that the coassembled state in the gel form is produced by the supramolecular interaction between the NDI-based bola-amphiphile and the long-chain amines. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy images reveal that the π-conjugated coassembled hydrogels exhibit nanofibrillar network morphologies. Interestingly, the coassembled hydrogels exhibit an enhanced fluorescence emission, excited-state lifetime, and quantum yield when compared with those of the NDI-containing amphiphile alone in its self-assembled state in aqueous medium. Moreover, the thermal stability and mechanical strength of these gels have been successfully tuned by varying the alkyl chain length of the corresponding amine. Moreover, these NDI-peptide-conjugated soft materials exhibit semiconducting behavior in their respective coassembled states. This holds future promise to use these peptide-appended NDI-based coassembled soft materials for applications in optoelectronic and other devices.

Fluorescence from an H-aggregated naphthalenediimide based peptide: photophysical and computational investigation of this rare phenomenon

Fluorescence associated with J-aggregated naphthalenediimides (NDIs) is common. However, in this study an NDI based synthetic peptide molecule is found to form a fluorescent H-aggregate in a chloroform (CHCl3)-methylcyclohexane (MCH) mixture. An attempt has been made to explain the unusual fluorescence property of this H-aggregated NDI derivative. Time correlated single photon counting (TCSPC) shows that the average lifetime of the NDI based molecule is on the order of a few nanoseconds. It is revealed from the computational study that the transition from the second exited state (S2) to the ground energy state (S0) is responsible for the fluorescence as S1 is a dark state. Such rare violation of Kasha's rule accounts for the unusual fluorescence properties of this type of NDI molecule in the H-aggregated state.

T-shaped monopyridazinotetrathiafulvalene-amino acid diad based chiral organogels with aggregation-induced fluorescence emission

A series of pyridazine coupled tetrathiafulvalene T-shaped derivatives with varying amino acid moieties have been synthesized and their gelation properties were studied in various organic solvents. Among these derivatives, two gelators bearing glycine or phenylalanine units display efficient gelation in aromatic and polar solvents. Interestingly, these gelators, except for the gelator containing two tryptophan units, are able to gel DMF via a solution-to-gel transformation when triggered with sonication for less than 20 s or cooled below zero. A number of experiments revealed that these gelator molecules self-assembled into elastically interpenetrating three-dimensional chiral fibrillar aggregates. Importantly, all of the resulting gels result in a dramatic enhancement of the fluorescence intensity compared with their hot solution in spite of the absence of a conventional fluorophore unit and the fluorescence was effectively quenched by the introduction of C60. Moreover, the gelators can be utilized for the removal of different types of toxic molecules, such as aromatic solvents and cationic dyes, from wastewater.

Spectroscopic differentiation between monomeric and aggregated forms of BODIPY dyes: Effect of 1,1-dichloroethane

1,1-Dichloroethane (1,1-DCE) can induce spectroscopic differentiation between aggregated and monomeric forms of BODIPY dyes.

H-bonding directed programmed supramolecular assembly of naphthalene-diimide (NDI) derivatives

In this review we have collated various supramolecular designs, all surrounding H-bonding among well-known functional groups (peptides, nucleic acids, amides, ureas, carboxylic acids, pyridine-hydroxyls, urethanes, imides and others), to dictate self-assembly of naphthalenediimide (NDI) π-systems (both small molecules and polymeric building blocks) that exhibit several exciting features including strong propensity for π-π interactions, π-acidity, excellent n-type semiconductivity, CT-complexation, ion-π interactions, ring-substitution dependent redox properties and photophysical properties. This article reveals that H-bonding can indeed serve as a very powerful and versatile tool to programmed self-assembly of a single or multiple dye system producing a wide range of tailored soft materials, including fibrillar gels, chromonic mesophases, foldamers, nanotubes, vesicles, reverse micelles and polymersomes, both in water and organic medium with distinct photophysical properties, charge transport properties, conductivity properties and functional group displays that are highly relevant in the fields of biology and organic electronics.

Photophysical properties of di-Schiff bases: evaluating the synergistic effect of non-covalent interactions and alkyl spacers in enhanced emissions of solids

Di-Schiff bases with alkyl spacer (ethyl, butyl and hexyl) showed enhanced light emitting properties in solid state, while quenching was observed for di-Schiff bases with hydrazine spacer. Packing of the molecules via non covalent interactions along with the flexible spacer played the role in dictating the emission properties.

Self-assembly of fluorescent diimidazolium salts: tailor properties of the aggregates changing alkyl chain features

Self assembly of fluorescent diimidazolium NDI salts showed properties of aggregates changing with alkyl chain length, with an odd–even effect.

Bis-naphthalimides bridged by electron acceptors: optical and self-assembly characteristics

The self-assembly of small organic molecules into molecular stacks plays a vital role in the construction of stable supramolecular structures.

Synthesis of multi-functional materials through self-assembly of N-alkyl phenothiazine linked poly(aryl ether) dendrons

Multi-functional materials developed from low molecular weight dendron gelators for phase selective gelation, a hydrophobic surface and invisible ink-gel formation.

Multi-stimuli responsive fluorescent behaviors of a donor–π–acceptor phenothiazine modified benzothiazole derivative

Donor–π–acceptor type phenothiazine modified benzothiazole derivative PVBT exhibited multi-stimuli responsive fluorescent properties.

Photo-triggered transformation from vesicles to branched nanotubes fabricated by a cholesterol-appended cyanostilbene

Vesicles constructed from cholesteryl cyanostilbene could transform into nanotubes upon UV light irradiation, in which the photoluminescence could be fine-tuned.

Nanofibrous hydrogels self-assembled from naphthalene diimide (NDI)/amino acid conjugates

A new approach is proposed for the design of NDI-capped supramolecular hydrogels.

Remarkable influence of alkyl chain lengths on supramolecular hydrogelation of naphthalene diimide-capped dipeptides

The influence of aliphatic chain lengths on supramolecular hydrogelation of naphthalene diimide-capped dipeptides is described.